I bought the fitbit charge HR in the summer of 2016 and it gave me these same burns/rash within weeks of wearing it every day. With this fitbit I got the rash only under the HR monitor and by the buckle. I used wipes to clean it after I worked out, never wore it in the summer, but still thought it had something to do with something I had done to it. I never figured out what it was, but I returned it at Costco. I then bought the Charge 2 for Christmas in 2016 and I was SO excited. I really missed counting my steps and calories, as well as other functions the fitbit has to offer. When I got my new fitbit, I was determined to do EVERYTHING right. I cleaned it with a wipe all the time, took it off periodically to sleep or just to let my wrist breathe, transferred the band to my other wrist, you name it. I am sad to report that I got the same burns, but this time all around my wrist. I was so upset because I love my fitbit. I use it for hot yoga, regular yoga, running, lifting, everything. I don't know what to do now because I want to keep using it or something similar, and I also don't want to return it because this time I bought it directly from the fitbit website, so shipping it all the way back would be a hassle. Overall, not happy but lazy and I still like it!
P.S. - i AM SO GLAD i found this forum. I didn't really tell anyone about the old one I had because I didn't know anyone else who had one or who had this reaction, and again, I thought it was my fault. Definitely don't think so anymore.